JPH08210964A - Prediction Method of Diffusion Coefficient of Noncondensable Gas in Aromatic Polyimide Film - Google Patents

Abstract

(57) [Abstract] [Purpose] In an aromatic polyimide film that enables the estimation of the gas permeability coefficient of non-condensable gases without the actual production of the aromatic polyimide film and the experimental operation of the gas permeability coefficient. To provide a method for estimating the gas diffusion coefficient of. [Structure] The molecular structure of the aromatic polyimide molecule of the aromatic polyimide film is divided into unit elements, and the cohesive energy and molar volume of each unit element are calculated,
Next, the cohesive energy density is calculated from the cohesive energy and the molar volume of each of the calculated unit elements, and further, this cohesive energy density and the non-condensable gas of the non-condensable gas also calculated from the cohesive energy and the molar volume of each unit element A method for estimating the diffusion coefficient of a non-condensable gas in an aromatic polyimide film, which comprises calculating the gas diffusion coefficient from the cohesive energy density.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for estimating the diffusion coefficient of a non-condensable gas in an aromatic polyimide film.
More specifically, the present invention relates to a method for estimating the diffusion coefficient of a non-condensable gas in an aromatic polyimide film that can be used for estimating the gas permeability coefficient of an aromatic polyimide film.

[0002]

2. Description of the Related Art Aromatic polyimide films are used for various purposes by utilizing their excellent heat resistance and chemical resistance. Among such applications, there is an application of a gas separation membrane used in a form in which a porous membrane is attached to one side or both sides of an aromatic polyimide film. That is, the aromatic polyimide film, utilizing its high heat resistance and chemical resistance,
It is used as a highly durable asymmetric or symmetric gas separation membrane for separating gas or organic matter. When used as such a gas separation membrane, the gas permeability coefficient of the aromatic polyimide film itself becomes a problem. Although the gas permeability coefficient of such an aromatic polyimide film can be measured by an experimental operation, it is necessary to manufacture aromatic polyimide films having various molecular structures and measure the gas permeability coefficient for each of them. Is a difficult task. Therefore, without performing the actual production of the target aromatic polyimide film and the experimental operation of the gas permeability coefficient,
If the gas permeability coefficient can be estimated, it is obvious that the design of the aromatic polyimide film having the necessary gas permeability coefficient (design of the molecular structure) will be facilitated.

The relationship between the gas permeability and the chemical structure of a polymer film has been studied so far, and for example, the idea of explaining the diffusion of gas in a polymer film from the free volume of the polymer is effective. Met. As a representative of such an idea, Fujita's free volume theory, which theoreticalizes gas diffusion in a rubber-like polymer material, is known (M. Goldstein: "Amorphous Material".
s ", Willy-Interscience, London, 1972). And, there are many published examples of applying this idea to glassy polymer materials. However, this theory has a high correlation in part. Although often seen, the problem is that the correlation is not sufficient when broadly explaining the structure and permeability of the glassy polymer film. It was found that even if the above concept was used to estimate the gas permeability coefficient of the aromatic polyimide film, the correlation with the gas permeability coefficient of the actually produced aromatic polyimide film was insufficient.

[0004]

In an aromatic polyimide film that enables the estimation of the gas permeability coefficient of a non-condensable gas without actually manufacturing the aromatic polyimide film and performing an experiment operation of the gas permeability coefficient. An object of the present invention is to provide a method for estimating the gas diffusion coefficient of.

[0005]

Means for Solving the Problems The present invention divides the molecular structure of aromatic polyimide molecules of an aromatic polyimide film into unit elements, calculates each cohesive energy and molar volume for each unit element, and then calculates The cohesive energy density is calculated from the calculated cohesive energy and the molar volume of each unit element, and the cohesive energy density is also calculated from the cohesive energy and the molar volume of each unit element. It is a method of estimating the diffusion coefficient of a non-condensable gas in an aromatic polyimide film by calculating the gas diffusion coefficient from the energy density.

That is, the present invention divides the molecular structure of the aromatic polyimide molecule of the aromatic polyimide film into unit elements, calculates each cohesive energy and molar volume for each unit element, and utilizes these. , Calculates the cohesive energy density of the aromatic polyimide film, and from this value, the cohesive energy density of the non-condensable gas calculated in the same manner to estimate the gas diffusion coefficient of the non-condensable gas in the aromatic polyimide film Method, the gas diffusion coefficient thus obtained shows a high correlation between the already known gas permeability coefficient of a polymer film and the diffusion coefficient of a non-condensable gas in the polymer film. It can be used to estimate the gas permeability coefficient of an aromatic polyimide film.

Next, the method for estimating the diffusion coefficient of the non-condensable gas in the aromatic polyimide film of the present invention will be described in detail. The aromatic polyimide film which is the object of the estimation of the diffusion coefficient of the present invention is already known and, as described above, is used for various purposes including the use of the gas separation membrane. Therefore, the aromatic polyimide film to be estimated in the present invention is not particularly limited.

Gases for which the diffusion coefficient in an aromatic polyimide film can be estimated according to the present invention are non-condensable gases (eg,
Hydrogen, nitrogen, argon, carbon monoxide, carbon dioxide). That is, a condensable gas (eg, steam, hydrogen sulfide gas, sulfurous acid gas) causes condensation in the film due to environmental conditions such as temperature, so it is necessary to incorporate a factor due to such condensation in the diffusion coefficient, In the method of calculating from the cohesive energy and the molar volume of each unit element of the molecular structure of the aromatic polyimide molecule clarified in the present invention, it is difficult to obtain a gas diffusion coefficient having a high degree of approximation. On the other hand, in a non-condensable gas, since its diffusion characteristics do not depend so much on the environmental conditions, it has a high approximation by the molecular structure of the aromatic polyimide film and the estimation method of the present invention based on the molecular structure of the non-condensable gas. The diffusion coefficient can be calculated.

The molecular structure of a macromolecular substance composed of repeating units is divided into unit elements, the cohesive energy and the molar volume of each unit element are calculated, and then the calculated cohesion of each unit element is calculated. A method of calculating the cohesive energy density (hereinafter, sometimes referred to as CED) from energy and molar volume is already known as a calculation method of Fedor (DWVanKrevelen and PJHoft).
yzer, "Properties of Polymers, 2nd., Elsevier Amster
dam (1976), Chap. 4, and "Basics of Synthetic Membranes" Takeshi Matsuura, Kitami Shobo, 1981). The molecular structure of the aromatic polyimide in the present invention is divided into unit elements, each cohesive energy and molar volume are calculated for each unit element, and then coagulated from the calculated cohesive energy and molar volume of each unit element. The method of calculating the energy density can be performed by utilizing such a known method. If only one repeating unit is used, CE
D may be calculated according to the Fedor formula, and when there are two or more repeating units, CED is calculated for each repeating unit, and the CED is distributed and calculated according to the mole fraction of each repeating unit. be able to.

That is, the cohesive energy density (CED _pi ) of the aromatic polyimide can be calculated by the following formula. CED _pi = ( _{ΣE cohi} / _{ΣV i} ) [E _cohi represents the cohesive energy per mole, and V _i represents the molar volume. Also, the cohesive energy density of the non-condensable gas can be calculated by using a similar method based on its molecular structure.

From the cohesive energy density of the aromatic polyimide obtained by the above method and the cohesive energy density of the non-condensable gas, the gas diffusion coefficient (D) can be obtained by the following equation for carbon dioxide. it can. D = 7.6 × 10 ⁻⁶ × (T / 273.15) × exp
(-22.1 × CED _pi / RT) [R represents a gas constant (J / mol · K), T represents an absolute temperature (K), and CED _pi represents a cohesive energy density (J / mol) of an aromatic polyimide. . In addition, "7.6 x 1
“0 ⁻⁶ ” and “−22.1” are numerical values determined by the type of gas (these numerical values are the numerical values in the case of carbon dioxide). The method for calculating the gas diffusion coefficient (D) of this polymer substance is described in detail in the following document. "Performance evaluation method for artificial membranes" (Kitami Shobo, 1985)

From the gas diffusion coefficient obtained as described above, the gas permeation amount (Q) in the aromatic polyimide film can be determined as follows. First,
The gas permeability coefficient P (time constant) is calculated from the diffusion coefficient (D) and the solubility coefficient (S) by the following formula. P = D × S The solubility coefficient (S) is a coefficient determined by the type of gas and the polymer substance of the film material, but the influence of the type of polymer substance is small. This solubility coefficient (S) can be calculated from the permeation coefficient and diffusion coefficient by the polymerization method or the method described in the above “Method for evaluating performance of artificial membrane”.

The gas permeation amount (Q) is determined by the above-mentioned permeation coefficient P.
Can be calculated according to the following formula. Q = P (p ₁ −p ₂ ) A · t / L [P is the transmission coefficient, p ₁ and p ₂ are the pressures on both sides of the film (p ₁ is the sending side, and p ₂ is the discharging side), A is Film area, t is time, and L is film thickness. ]

[0014]

【Example】

 Example 1 The following repeating unit:

[0015]

Embedded image

For the aromatic polyimide having
According to the calculation method of dor, it is divided into the following structural units,
Cohesive energy (E _cohi : J / mol) and molar volume (V
_i : cm ³ / mol)
CED _pi (cohesive energy density) was obtained, and D (gas permeability coefficient) of carbon dioxide was calculated. Structural unit E _cohi V _i (a) × 2 4190 × 2 (−9.0) × 2 (b) × 4 17370 × 4 10.8 × 4 (c) × 2 31940 × 2 33.4 × 2 (d ) × 2 31940 × 2 52.4 × 2 (e) × 1 4940 × 1 16.1 × 1 Σ E _cohi = 210560 Σ V _i = 212.9

CED _pi = ( _{ΣE cohi} / ΣV _i ) = 989.0 The above CED _{pi is obtained} by the following equation: D = 7.6 × 10 ⁻⁶ × (T / 273.15) × exp
Substituting into (-22.1 × CED _pi / RT) (temperature 35 ° C.), D = 1.7 × 10
^-9 is obtained. In order to compare the calculated value with the measured value, a high vacuum time lag method is used under the same conditions [see "Method for evaluating performance of artificial membrane" (Kitami Shobo, 1985)].
When D (gas permeation coefficient) was actually measured by D, D = 1.
5 × 10 ⁻⁹ was obtained. From the above results, it can be seen that the method for estimating the gas permeation coefficient of the present invention agrees well with the actually measured value.

Example 2 The following repeating unit:

[0019]

Embedded image

For the aromatic polyimide having
According to the calculation method of dor, it is divided into the following structural units,
Cohesive energy (E _cohi : J / mol) and molar volume (V
_i : cm ³ / mol)
CED _pi (cohesive energy density) was obtained, and D (gas permeability coefficient) of carbon dioxide was calculated. Structural unit E _cohi V _i (f) × 2 4190 × 2 (−9.0) × 2 (g) × 4 17370 × 4 10.8 × 4 (ch) × 2 31940 × 2 33.4 × 2 (li ) × 4 31940 × 4 52.4 × 4 (nu) × 3 3350 × 3 3.8 × 3 Σ E _cohi = 279550 Σ V _i = 309.2

CED _pi = (Σ E _cohi / Σ V _i ) = 904.1 The above CED _{pi is obtained} by the following equation: D = 7.6 × 10 ⁻⁶ × (T / 273.15) × exp
Substituting for (-22.1 × CED _pi / RT) (temperature 35 ° C.), D = 3.5 × 10
^-9 is obtained. In order to compare this calculated value with the measured value, D was measured by the high vacuum time lag method under the same conditions.
When the (gas permeability coefficient) was actually measured, D = 3.5 × 10
^-9 was obtained. From the above results, it can be seen that the method of estimating the gas permeation coefficient of the present invention agrees well with the actually measured value.

[Example 3] The following acid components:

[0023]

Embedded image And the following two diamine components:

[0024]

[Chemical 4]

[0025]

Embedded image

Is a molar ratio :: (acid component of Chemical formula 3: diamine component of Chemical formula 4: diamine component of Chemical formula 5) The aromatic polyimide copolymerized into the following structural units according to the calculation method of Fedor, Cohesive energy (E _cohi : J / mol) and molar volume (V _i : cm ³ / m)
ol) and CED _pi (cohesive energy density) were obtained, and D (gas permeation coefficient) of carbon dioxide was calculated. Structural unit E _cohi V _i (ru) × 1 1470 × 1 (−19.2) × 1 (e) × 2 4270 × 2 57.5 × 2 (wa) × 2 4190 × 2 (−9.0) × 2 (F) × 4 17370 × 4 10.8 × 4 (Yo) × 2 31940 × 2 33.4 × 2 (T) × 2 × 0.6 31940 × 4 × 0.6 52.4 × 2 × 0 .6 (re) × 1 × 0.6 4940 × 1 × 0.6 16.1 × 1 × 0.6 (so) × 2 × 0.4 31940 × 2 × 0.4 14.4 × 2 × 0 .4 (tsu) × 1 × 0.4 20850 × 1 × 0.4 19.6 × 1 × 0.4 (ne) × 2 × 0.4 11550 × 2 × 0.4 24.0 × 2 × 0 .4 (na) having five rings 1050 × 1 × 0.4 16.0 × 1 × 0.4 Σ E _cohi = 236594 Σ V _i = 305.3

CED _pi = (Σ E _cohi / Σ V _i ) = 774.96 The above CED _{pi is obtained} by the following equation: D = 7.6 × 10 ⁻⁶ × (T / 273.15) × exp
Substituting for (-22.1 × CED _pi / RT) (temperature 35 ° C.), D = 1.2 × 10
^-8 is obtained. In order to compare this calculated value with the measured value, D was measured by the high vacuum time lag method under the same conditions.
When the (gas permeability coefficient) was actually measured, D = 2.3 × 10
^-8 was obtained. From the above results, it can be seen that the method for estimating the gas permeability coefficient of the present invention is in good agreement with the actually measured value for the aromatic polyimide copolymer.

[0028]

The method for estimating the diffusion coefficient of a non-condensable gas in an aromatic polyimide film of the present invention allows the production of the aromatic polyimide film and the gas permeability coefficient thereof without any experimental operation. The estimation of is realized with high accuracy.

Claims (1)

[Claims] 1. A molecular structure of aromatic polyimide molecules of an aromatic polyimide film is divided into unit elements, each cohesive energy and molar volume of each unit element is calculated, and then each calculated unit element is calculated. The cohesive energy density is calculated from the cohesive energy and the molar volume, and the gas diffusion coefficient is calculated from the cohesive energy density and the cohesive energy density of the non-condensable gas similarly calculated from the cohesive energy and the molar volume of each unit element. A method of estimating the diffusion coefficient of a non-condensable gas in an aromatic polyimide film, which comprises calculating.